17 



idly and with slight fatigue, they can ordinarily spare sufficient time 

 by the way for brief stops in places where food is abundant and easily 

 obtained. * * * Excellent examples are the Robin, Horned Lark and 

 most Icteridfe. Birds of easy, tireless wing, which habitually feed in the 

 air or over very extensive areas, migrate exclusively by day, because, 

 being able either to obtain tlieir usual supply of food as they fly, or 

 to accomplish the longest journeys so rapidly that they do not require 

 to feed on the way, they are under no necessity of changing their 

 usual habits. The best examples are Swallows, Swifts and Hawks. 

 Nocturnal and crepuscular birds, at least migratory species, are all 

 strong-winged and accustomed to seek their food over wide areas. 

 Hence, like Swallows, Swifts and Hawks, they migrate during the 

 hours of their habitual activity." 



Day migrants perform their journeys either as scattered individuals 

 or in compact flocks, there being comparatively little mixture of 

 species. As regards night migrants, however, the case is different. 

 All the species which are migrating on any particular night, being 

 attracted V)y each other's notes,* become more or less mingled 

 together in an immense column, not forming a compact flock but com- 

 posed of individuals and small bunches flying sufficiently near to one 

 another to be guided by the chirping of those just ahead. Ol)serva- 

 tions made from lighthouses seem clearly to show this to be the 

 nature of the night migrations, and it is really most natural, being 

 merely a continuation of the actions of these same birds while feed- 

 ing in the woodland during the day; when they go shifting from tree 

 to tree, the various species intermingled and all slowly following the 

 lead of those just ahead of them. The leaders of these migratory 

 flights are probably old birds which have had the experience of pre- 

 vious migrations and have thoroughly learned the route of travel. 

 The experience of most of the leading ornithologists of this country, 

 however, seems to show that the old birds of most if not all species 

 migrate southward before their young, leaving the nesting-ground 

 soon after the moult is completed and entrusting their young to the 

 guidance of later migrants, often belonging to quite different species. 



Migrating birds seem to follow the same course year after year, so 

 that it is possible to map out pretty exactly their principal lines of 

 flight, and this has been actually done in Europe, where the matter 



* Birds migrating by night keep up a continual chirping, a kind of calling 

 and answering as it were, to avoid being separated from each other. This can 

 often be distinctly heard as they pass overhead. 



